Abstract: In order to set up an evaluation method of measurement uncertainty for the determination of nitrate in karst underground water by the ion chromatographic detection technology, the continuous propagation model of uncertainty is used. The differences among different regression methods are also discussed. The results show that:(1) the main sources of measurement uncertainty come from the sub-uncertainties of calibration solutions, calibration curve fitting and measurements process. (2) different regression methods have different effects on the uncertainty evaluated at different levels. The lower the nitrate content in underground water is, the greater the different is. In addition, based on the quantitative analysis of each uncertainty component through experimental results, the standard uncertainty model for nitrate determination results is obtained.